Ecology is the study of how organisms biotic interact with each other and their environment abiotic

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• Chapter 53

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• Ecology is the study of how organisms (biotic)
  interact with each other and their environment
  (abiotic)

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Populations

• A population consists of individuals of a species
  living together at the same place at the same
  time.
• Most species have a limited geographic range.
• organisms environment (abiotic) include
• temperature
• water
• sunlight
• soil

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Population Dispersion

• Randomly spaced
• Uniformly spaced - competition for resources
• Clumped spacing - unequal resources

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Population Dispersion

• Human effect
• Dispersal mechanisms
• light seeds (wind)
• hooks and hairs (animal fur)
• fruits (animal digestive systems)

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Demography

• Demography - statistical study of populations
• Survivorship curves
• Survivorship is the percentage of an original
  population that survives to a given age.
• Type I - full life span
• Type II - mortality unrelated to age
• Type III - early susceptibility

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Cost of Reproduction

• A life history is the complete life cycle of an
  organism.
• cost of reproduction
• Due to limited resources, increased reproduction
  may decrease survival
• Natural selection will favor the life history
  that maximizes reproductive success.
• number of offspring vs size
• size may affect chances of survival

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Cost of Reproduction

• Reproductive events per lifetime
• semelparity - organisms focus all reproductive
  efforts on a single, large event
• iteroparity - organisms produce offspring several
  times over many seasons
• Age at first reproduction
• Longer-lived animals tend to reproduce later, and
  provide more parental care than shorter-lived
  animals.

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Biotic Potential

• Exponential growth model - J curve
• Rate at which a population will increase when no
  limits are placed on the rate of growth.

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Biotic Potential

• Carrying capacity
• Carrying capacity (K) is the maximum number of
  individuals the resources in a given area can
  support.
• Logistic growth
• As a population approaches carrying capacity, its
  growth rate slows as resources become depleted.
• sigmoidal (S curve) growth curve

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Population Growth
Density-dependent population controls As
populations approach their carrying capacity,
competition for resources can be severe, leading
to decreased birth rate and increased risk of
mortality.
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Linked Population Cycles
Population cycles snowshoe hares Food plants
(willows) and predators (lynx) both control the
population.
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Population Growth and Life History Models

• K-selected species tend to produce relatively
  few, large offspring.
• large investment in parental care
• r-selected species tend to produce many, small
  offspring.
• small investment in parental care